Less is more: 25uF instead of 50

[Colas LeGrippa]

Hola amigos,


I just finished building an amplifier which power supply is based on the Marshall 2204.
In that particular model, the power tubes screens are fed by a 50uF capacitor and so are the PI,  CF and preamp tube.
The JCM 800 is different. While there are the same number of 50uF capactors (6), the screens are fed by two 50uF in parallel (100uF),
while the CF and preamp are fed by the same 50uF cap.
I find that the tone of the 2204 is too tight compared to the JCM 800 which is warmer, softer. I recall having read a long time ago about feeding the preamp tubes with low uF caps, like 10 or 20. That's what I had put  in one of my builds which  tone is better compared to my new one.
Any comments on that ?


Colas LeGrippa

[sluckey]

I find that the tone of the 2204 is too tight compared to the JCM 800 which is warmer, softer.
Any comments on that ?

The JCM 800 is a whole series, not just a single amp. The 2204 50 watt amp is part of the JCM 800 series.

When you say JCM 800 which specific amp are you referring to? The JMP 1987 50 watt amp fits your description as far as filter caps are concerned. The 1987 also has one less gain stage so naturally it would sound warmer even if the filter caps were the same as a 2204.

[Colas LeGrippa]

Right on Sluckey, it is the 50 watts 1987 model. Thanks for the small tutorial on Marshall jcm800 series




I don t understand , if the 2204 is part of the JCM800 series, why in the schematics library it appears to be something totally different.


Anyway, I think you got my point that I prefer low filter caps values in  the preamp section, like Fender used to do. It makes an amp sings, more or less like a tube rectifier does, inducing a kind of sag.


From the other side, I can' t hear no difference between screens fed by 100  or 50uF caps.


Colas

[sluckey]

I don t understand , if the 2204 is part of the JCM800 series, why in the schematics library it appears to be something totally different.

There are several 2204 schematics in the library. They are all the same, just drawn differently. Here's the one I like to use...
   
     https://el34world.com/charts/Schematics/files/Marshall/Marshall_jcm800_2204_lead_series.pdf

Which specific schematic is confusing you?

[Colas LeGrippa]

Sorry for my lack of knowledge on Marshall amps.
The jcm800 model 4010 is different:


100uF on the screens, Pi and CF on the same 50 uF. Weird, no ?  , considering that he PI is part of the amplifier section.


I had never realized that the 2204 was included in the JCM800 series ...


Colas (shame on me, I won t tell Linda to  preserve my good reputation)